Ceramic composites comprised of silicon carbide whiskers and alumina powder are well known to prior art. Thus, by way of illustration, U.S. Pat. No. 4,543,345 discloses a silicon carbide whisker-alumina ceramic composite with good fracture toughness. U.S. Pat. No. 4,652,413 discloses that silicon carbide whisker-reinforced alumina ceramic articles are useful as structural materials for the fabrication of turbocharger rotors, cylinders, bearings, and other components of heat engines.
One problem with the ceramic composites presently available is that they cost from about twenty to about fifty dollars per pound, a price which makes them too expensive for certain applications.
In 1987, applicant George T. Hida disclosed a process for preparing a silicon carbide-whisker/alumina composite. In his Ph.D. Thesis, which was entitled "Study of Solid-State Aluminothermal Reactions: Influence of Activation and Moderation Processes," which was submitted to the senate of the Technicron--Israel Institute of Technology in Haifa, Israel in Feb. of 1987, and which was published in Apr. of 1987, a reaction was disclosed in which three moles of silica were reacted with four moles of aluminum and 3 moles of carbon. The silica reagent was 200/230 mesh fraction quartz sand; the aluminum reagent was -325 mesh aluminum powder; and the carbon reagent was carbon black. Stoichiometric amounts of these reagents were mixed, the mixture was compacted into pellets by cold pressing in a die, and the pressed pellets were placed into a furnace which had been preheated to 720 degrees centigrade and were thereafter ignited.
The process disclosed in Hida's 1987 thesis was a substantial improvement over prior art processes for preparing silicon carbide whisker/alumina composite materials. However, it did not reduce the cost of making the composite down to commerically suitable levels.
It is an object of this invention to provide a process for preparing a heat-treated silicon carbide whisker/alumina composite with improved properties at a cost which is substantially cheaper than is currently possible.